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<h1>Error: ngRepeat:dupes
  <div><span class='hint'>Duplicate Key in Repeater</span></div>
</h1>

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    <pre class="minerr-errmsg" error-display="Duplicates in a repeater are not allowed. Use 'track by' expression to specify unique keys. Repeater: {0}, Duplicate key: {1}, Duplicate value: {2}">Duplicates in a repeater are not allowed. Use 'track by' expression to specify unique keys. Repeater: {0}, Duplicate key: {1}, Duplicate value: {2}</pre>
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<h2>Description</h2>
<div class="description">
  <p>Occurs if there are duplicate keys in an <a href="api/ng/directive/ngRepeat">ngRepeat</a> expression.  Duplicate keys are banned because AngularJS uses keys to associate DOM nodes with items.</p>
<p>By default, collections are keyed by reference which is desirable for most common models but can be problematic for primitive types that are interned (share references).</p>
<p>For example the issue can be triggered by this <em>invalid</em> code:</p>
<pre><code>&lt;div ng-repeat=&quot;value in [4, 4]&quot;&gt;&lt;/div&gt;
</code></pre>
<p>To resolve this error either ensure that the items in the collection have unique identity or use the <code>track by</code> syntax to specify how to track the association between models and DOM.</p>
<p>The example above can be resolved by using <code>track by $index</code>, which will cause the items to be keyed by their position in the array instead of their value:</p>
<pre><code>&lt;div ng-repeat=&quot;value in [4, 4] track by $index&quot;&gt;&lt;/div&gt;
</code></pre>

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